Articles made from reinforced plastics can be formed by a number of processes. For example glass reinforced polyester articles can be produced by a variety of well known methods, such as hand lay-up, spray-up, resin injection, vacuum impregnation, cold press moulding, filament winding and hot press moulding.
Glass fibre is the commonest reinforcement, but other fibres both natural and synthetic, mineral or organic can be used, such as asbestos, carbon fibre, sisal or polyester.
The usual matrix is an unsaturated polyester resin, but epoxy or vinyl ester resins or other resin capable of curing at low temperatures by an addition mechanism are also used.
In these mouldings it is often desired to locate extra reinforcement or inserts in specific places so that added strength added stiffness or fixing points are provided. This is sometimes difficult as the reinforcement can move during the moulding process either during preparation, through mould closure or by flow of the resin.